In the most specific sense, Control means this:https://en.wikipedia.org/wiki/Control_(linguistics)When a verb like "decide" controls the subject of an embedded clause: "I decided to eat something." where the embedded subject is the same as the higher subject. It is controlled by it.

But the term might be used more generally to refer to other ideas like argument selection (a verb controls its object?), or maybe structural relationships like c-command or dominance.

Again, like your other questions, these things must be defined somewhere in your textbook, with examples.